全文获取类型
收费全文 | 53274篇 |
免费 | 5016篇 |
国内免费 | 2677篇 |
专业分类
电工技术 | 3631篇 |
技术理论 | 5篇 |
综合类 | 3790篇 |
化学工业 | 8962篇 |
金属工艺 | 2538篇 |
机械仪表 | 3043篇 |
建筑科学 | 4582篇 |
矿业工程 | 1439篇 |
能源动力 | 1404篇 |
轻工业 | 4845篇 |
水利工程 | 1021篇 |
石油天然气 | 2584篇 |
武器工业 | 483篇 |
无线电 | 5987篇 |
一般工业技术 | 6666篇 |
冶金工业 | 2338篇 |
原子能技术 | 684篇 |
自动化技术 | 6965篇 |
出版年
2024年 | 242篇 |
2023年 | 967篇 |
2022年 | 1688篇 |
2021年 | 2267篇 |
2020年 | 1837篇 |
2019年 | 1452篇 |
2018年 | 1623篇 |
2017年 | 1783篇 |
2016年 | 1604篇 |
2015年 | 2206篇 |
2014年 | 2717篇 |
2013年 | 3308篇 |
2012年 | 3712篇 |
2011年 | 3860篇 |
2010年 | 3214篇 |
2009年 | 2985篇 |
2008年 | 3007篇 |
2007年 | 2788篇 |
2006年 | 2781篇 |
2005年 | 2436篇 |
2004年 | 1572篇 |
2003年 | 1400篇 |
2002年 | 1280篇 |
2001年 | 1141篇 |
2000年 | 1341篇 |
1999年 | 1327篇 |
1998年 | 1112篇 |
1997年 | 960篇 |
1996年 | 878篇 |
1995年 | 756篇 |
1994年 | 609篇 |
1993年 | 444篇 |
1992年 | 378篇 |
1991年 | 303篇 |
1990年 | 233篇 |
1989年 | 212篇 |
1988年 | 141篇 |
1987年 | 84篇 |
1986年 | 79篇 |
1985年 | 67篇 |
1984年 | 35篇 |
1983年 | 15篇 |
1982年 | 32篇 |
1981年 | 21篇 |
1980年 | 26篇 |
1979年 | 9篇 |
1976年 | 4篇 |
1970年 | 3篇 |
1959年 | 9篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 94 毫秒
31.
32.
江河湖海疏浚工程对于拓展和保障航运安全、促进生态恢复、维护/改善远海岛礁环境具有不可或缺的作用.目前,在绞吸和耙吸疏浚船上,多采用射线密度计及电磁流量计对输泥密度、产量等进行在线计量,并作为实现疏浚系统自动控制的重要参量.由于射线密度计潜在的人员健康、公共安全和环保风险,在一些国家和地区已建立了放射源的有序退出机制.电阻层析成像使用安装于管壁的电极阵列获得管道内流体的电导率分布,进而推导出管道内的泥浆密度,具有无辐射、全场测量及实时可视化的优点.电阻层析成像测量系统经过特殊设计,可适应从内陆淡水到海水的巨大电导率变化.初步测试表明,电阻层析成像测量数据与射线密度计具有良好一致性,具备了作为在线泥浆密度测量的可行性.此外,ERT可提供实时的流动成像,对于提高对疏浚管道监测能力和降低堵管概率具有重要意义. 相似文献
33.
As the development of cloud computing and the convenience of wireless sensor netowrks, smart devices are widely used in daily life, but the security issues of the smart devices have not been well resolved. In this paper, we present a new NTRU-type public-key cryptosystem over the binary field. Specifically, the security of our scheme relies on the computational intractability of an unbalanced sparse polynomial ratio problem (DUSPR). Through theoretical analysis, we prove the correctness of our proposed cryptosystem. Furthermore, we implement our scheme using the NTL library, and conduct a group of experiments to evaluate the capabilities and consuming time of encryption and decryption. Our experiments result demonstrates that the NTRU-type public-key cryptosystem over the binary field is relatively practical and effective. 相似文献
34.
35.
刘潜 《江汉石油职工大学学报》2015,28(1):102-103
本文介绍了江汉油田员工考勤管理工作的基本情况,梳理和分析了当前员工考勤管理中存在的问题及原因,提出了要进一步细化和完善管理制度,强化过程监督和责任落实,逐步推进考勤公示制度化等措施。 相似文献
36.
Shengyue Gu Shouyang Zhang Fei Liu Wei Li 《Journal of the European Ceramic Society》2018,38(15):5082-5091
Y2Hf2O7 possesses low thermal conductivity and high melting point, which make it promising for a new anti-ablation material. For evaluating the thermal stability and the potential applications of Y2Hf2O7 on anti-ablation protection of C/C composites, Y2Hf2O7 ceramic powder was synthesized by solution combustion method and Y2Hf2O7 coating was prepared on the surface of SiC coated C/C composites using SAPS. Results shown that the coating exhibits good ablation resistance under the heat flux of 2.4?MW/m2 with the linear and mass ablation rates are 0.16?μm?s?1 and ?0.028?mg?s?1, respectively, after ablation for 40?s. With the prolonging of the ablation time, the increasing thermal stress causes the increase of cracks. Moreover, the chemical erosion from SiO2 and the physical volatilization of low temperature molten products aggravate failure of the Y2Hf2O7 coating. 相似文献
37.
38.
39.
40.
High‐performance thermosets with tailored properties derived from methacrylated eugenol and epoxy‐based vinyl ester 下载免费PDF全文
Yuehong Zhang Yuzhan Li Vijay Kumar Thakur Zhenhua Gao Jiyou Gu Michael R Kessler 《Polymer International》2018,67(5):544-549
A renewable chemical, eugenol, is methacrylated to produce methacrylated eugenol (ME) employing the Steglich esterification reaction without any solvent. The resulting ME is used as a low‐viscosity co‐monomer to replace styrene in a commercial epoxy‐based vinyl ester resin (VE). The volatility and viscosity of ME and styrene are compared. The effect of ME loading and temperature on the viscosity of the VE–ME resin is investigated. Moreover, the thermomechanical properties, curing extent and thermal stability of the fully cured VE–ME thermosets are systematically examined. The results indicate that ME is a monomer with low volatility and low viscosity, and therefore the incorporation of ME monomer in VE resins allows significant reduction of viscosity. Moreover, the viscosity of the VE–ME resin can be tailored by adjusting the ME loadings and processing temperature to meet commercial liquid molding technology requirements. The glass transition temperatures of VE–ME thermosets range from 139 to 199 °C. In addition, more than 95% of the monomer is incorporated and fixed in the crosslinked network structure of VE–ME thermosets. Overall, the developed ME monomer exhibits promising potential for replacing styrene as an effective low‐viscosity co‐monomer. The VE–ME resins show great advantages for use in polymer matrices for high‐performance fiber‐reinforced composites. This work is of great significance to the vinyl ester industry by providing detailed experimental support. © 2018 Society of Chemical Industry 相似文献